New weight loss pill launched in Australia

A new medication to help fight obesity has been launched in Australia.

Contrave works on areas of the brain that control appetite and cravings.

It is the fourth medication to be approved in the country to help people with chronic weight problems.

Contrave works on the areas of the brain that control food cravings. (9news)

Melbourne physiologist Professor Michael Cowley developed the medication while working overseas after mapping key areas of the brain involved in the regulation of food intake.

The two ingredients naltrexone and bupropion are currently used separately in drugs to overcome substance abuse and to help quit smoking.

Professor Cowley said the two ingredients work on areas of the brain that help reduce hunger.

"We discovered that there were two places that these two drugs could interact and produce an effect on appetite, to reduce appetite, but also an effect on something called the reward centres to reduce what looked like food cravings," he said.

The effects of Contrave on weight loss, together with a reduced calorie diet and increased physical activity, were the subject of several trials.

In one trial, weight loss of at least 5 per cent baseline body weight was observed more frequently among patients treated with Contrave, compared with placebo.

Ingredients naltrexone and bupropion work together to control appetite cravings in the brain. (9news)

Weight loss was more pronounced in patients who completed 56 weeks of treatment.

"Five per cent weight loss isn't going to cause a dramatic change in the way people look but it does improve metabolic health," Professor Cowley said.

He said that includes decreasing the risk of heart attack and lowering the risk of diabetes and cholesterol conditions.

The common side-effects observed in trials were nausea, vomiting and constipation and there is the rare risk of seizures and suicidal thoughts.

People on the medication are asked to stop after 16 weeks, if they don't lose at least 5 per cent of their initial body weight.

Obesity expert, Professor John Dixon says the addition of Contrave gives doctors another opportunity to treat more people properly.

He says the 1.5 million Australians who are severely obese are not being treated effectively and are often blamed for lacking willpower.

He encouraged doctors to use the effective tools that are available to manage patients.

Contrave should only be taken for a maximum of 16 weeks as it has some side effects. (9news)

Another expert was cautious about the use of the medication. saying long-term safety data is limited.

"The medication would need to be taken on an ongoing basis and I don't think in all truth we know enough about the long-term use of these medications," University of Adelaide head of Medicine, Professor Gary Wittert said.

He said education on nutrition and physical activity have to be addressed before medication is looked at.

"For specific circumstances where some extra help is required, then the medication may find a place. But I don't think we know to be honest, enough about who's going to benefit most and under what circumstances," Professor Wittert said.

In Australia, Contrave is intended for adults who are obese or those with metabolic conditions caused by being overweight.